When attacking WEP/WPA/WPA2, I see people buy a wireless network adapter (e.g. Alfa). Why can't an inbuilt adapter in a laptop work? Or in other words, is there a quick way for me to check if the inbuilt adapter in my laptop could work for this attack? A simple command perhaps?
Relating to Baron's answer, he stands corrected with supporting packet injections, but they also need to support monitor mode too. For example, when I run:
airmon-g start wlan0 - This will convert my
mon1 depending on the interface chipset. Inbuilt can work, but they're sometimes not as powerful as they need to be and again, some don't support the correct requirements.
Usually the wireless adapter is unable to transmit in monitor mode and is restricted to a single wireless channel - source
To check if it supports monitoring mode, type
iwconfig and you'll see
wlan0 or something similar. If you have a pentesting distribution or the
aircrack package with
airodump etc. You can type
airmon-ng start wlan0 which will place your adapter into monitor mode and changing the interface from
mon0 or something similar.
Adding some more info on the channel limitation, see here.
When attacking WEP, I see people buy a wireless network adaptor (e.g., alfa). Why cant an inbuilt adapter in laptop work?
To be able to attack a wifi, your wireless interface/adapter have to support packet injection. here is a list of supported interfaces.
You can check if your wifi adapter support packet injection by putting the interface in monitor mode with